I used a couple of round 1cm (diameter) by 1 mm (thickness) magnets to keep the sphere in place, if you'd like to do the same print the basket_magnet and its cap, otherwise print the regular basket and leave the sphere empty. There is enough room to stack several magnets but i found that two are enough to keep the sphere in place unless the cube is shaken while upside down.

The prototype print required some vigorous sanding before the sides could actually fit together but in the end the whole thing stayed in one piece without glue. The files available here have been slightly resized to (hopefully) make things easier without compromising integrity, feedback is apreciated.

I printed everything at 0.12 with supports.